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Does foam contribute to structural integrity on catamaran hull?

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Does foam contribute to structural integrity on catamaran hull?

Old 02-10-2019, 04:56 AM
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I stand by what I said. The deck need to be supported. You could hang engines on that bare hull and it would go faster than with the deck in place due to less weight.

Looking at the construction the rear of the fuel tank bulkhead does need to be beefed up. More glass and or structure. Then the desired boxes need to be framed up, sides and bottoms made strong enough for the deck around them to be solid. Glass and Gelcoat. They are not there for hull integrity. See the Cat build for UCF. He has the boxes and lids you want to build. With pictures, material description, all you need to design your boxes. In fact the hull is brother to yours since it's same heritage.

I also have a KV hull 2001. Before they started foaming those made in USA.
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Old 02-10-2019, 08:18 PM
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52 gallons each or 196 liters
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Old 02-10-2019, 08:21 PM
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This one is a US made KC 2000 made in 1999 according to the paperwork. Got it from the second or third owner.

I am following the Horizon 3000 build you mention ...
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Old 02-10-2019, 08:24 PM
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I will be using Coosa baord as well. I have purchased 1/2". What thickness did you use? I want to keep the hull light.

It can go unlaminated. But I think I will laminate the underside too.
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Old 02-11-2019, 04:30 AM
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Picture of old floor and new Coosa board which was glassed on both sides. Top side is thicker.
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Old 02-11-2019, 05:59 AM
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Originally Posted by Jumpsummo View Post
The bulkheads are there to hold the deck up. The foam has zero structural value. Maybe a little sound deadening. Zero value and huge downside on resale if you put it back in Some KVs get waterlogged.
100%

Originally Posted by commuter boats View Post
And Boston Whalers don't work
Foam most certainly can be structural. Some catamarans have had issues, the structural loads aren't necessarily intuitive and I would suggest that there was nothing in the original construction it would be considered unnecessary. The only people that can answer your question are the people that built the boat or somebody that's capable of reengineering it.
Gerald
Boston Whalers work, but only if the Fiberglass is not compromised. Ive seen many commercial used Boston Whalers go to crap one the foam is breech-ed. Many foam cores today will not absorb water. But they have no structure value on their own.

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Old 02-11-2019, 06:05 AM
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Originally Posted by Danf View Post
Picture of old floor and new Coosa board which was glassed on both sides. Top side is thicker.
Coosa is awesome but its not pure air cell foam. Some will say its heavy, "I'll take it". Some say its bonding face to resign is not as much as foam, "I'll still take it". Structurally probably next best core to Marine plywood. I had my smaller crab boat built with Coosa, Its Awesome.

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Old 02-11-2019, 08:07 AM
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the amount of misinformation is comical. the bulkheads are there to hold the deck up but the foam has zero structural value? so if the foam is supporting the deck, how is it not structural? try supporting the deck with the fiberglass skin on each side of the foam and report back with the results.
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Old 02-11-2019, 08:14 AM
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People usually try to prove what they believe rather than believe what they prove. It's the scientific method.
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Old 02-11-2019, 08:55 AM
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Originally Posted by THE BARRACUDA View Post
100%

Boston Whalers work, but only if the Fiberglass is not compromised. Ive seen many commercial used Boston Whalers go to crap one the foam is breech-ed. Many foam cores today will not absorb water. But they have no structure value on their own.
Yeah, that's why they call it a composite, the glass and the foam worked together. They both contribute to the structure...
I think Coosa is way overrated and my opinion isn't based on having somebody do a job for me. You know the chemistry of the foam in Coosa is the same as the chemistry in the foam in a Boston whaler.
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Last edited by commuter boats; 02-11-2019 at 09:40 AM.
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Old 02-11-2019, 09:20 AM
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Originally Posted by pilotwerxs View Post
the amount of misinformation is comical. the bulkheads are there to hold the deck up but the foam has zero structural value? so if the foam is supporting the deck, how is it not structural? try supporting the deck with the fiberglass skin on each side of the foam and report back with the results.
The foam used in bulkheads is covered in fiberglass. It might be really sturdy foam to assist the fiberglass rigidity once its covered in fiberglass but the fiberglass is so much stronger than the foam the strength of the foam is barely counting.
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Old 02-11-2019, 09:25 AM
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Originally Posted by Jumpsummo View Post
The foam used in bulkheads is covered in fiberglass. It might be really sturdy foam to assist the fiberglass rigidity once its covered in fiberglass but the fiberglass is so much stronger than the foam the strength of the foam is barely counting.
its called a composites structure, they need each other to perform.
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Old 02-11-2019, 12:48 PM
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Originally Posted by tunnles View Post
American boats no wonder THE Chinese don't have many here ! they want boats that last !
Kevlacat is an Australian built boat in most instances. And a very well respected one at that. I realise a few moulds were sold to the US.

Tunnels, the pieces of crap fibreglass hulls they produce in China don't sell here due to the re-work and seaworthiness issues experienced here with them, even by the biggest factories that produce on contract for some of the overseas brands.

Last edited by Perthbloke; 02-11-2019 at 01:00 PM. Reason: More information
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Old 02-11-2019, 12:52 PM
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Originally Posted by paler View Post
My boat, a Kevlacat 2000, was completely filled with foam at the factory. It has a sealed deck with no compartments underneath.

After I ripped the floor out to replace it, I also removed the foam. I am considering to make some below deck storage with access hatches.

At the moment, I am concerned with the following:

- does the foam contribute to any structural reinforcement?
- will removing the bulkhead shown below affect structure?

I have been advised that the only reason that boats under 20 feet are foam filled us due to a USCG requirement. I cannot attest to that. Regardless I am overseas and do not need to comply with such regulation.

In case of emergency I have a Viking rescue raft. So the issue at hand is regarding structural integrity.


If I remove this bulkhead there will be room for dry storage or kill box.


If it is removed the unsupported span fwd to aft is almost equal to the fuel tank´s area span, around 44".


The bulkhead is quite thin, around 1/8
Try sending an email to info@kevlacat.com.au He's quite a nive bloke and will give good advice. Also, there is another place that specialises in the manufacture and refurbishment of cats that size. Explain to them and where you are and he will give great advice: https://www.facebook.com/Dna-Fibregl...562/?ref=br_rs
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Old 02-11-2019, 05:08 PM
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Originally Posted by pilotwerxs View Post
the amount of misinformation is comical. the bulkheads are there to hold the deck up but the foam has zero structural value? so if the foam is supporting the deck, how is it not structural? try supporting the deck with the fiberglass skin on each side of the foam and report back with the results.
The foam is there to control flexibility within the fiberglass. The fiberglass can hold it without the foam.

Originally Posted by commuter boats View Post
Yeah, that's why they call it a composite, the glass and the foam worked together. They both contribute to the structure...
I think Coosa is way overrated and my opinion isn't based on having somebody do a job for me. You know the chemistry of the foam in Coosa is the same as the chemistry in the foam in a Boston whaler.
Gerald
The only foam I've seen inside Boston whalers has been pored foam. I have not seen what they use on the Large 30Ft plus vessels. The foam and glass intertwined and fused together in Coosa is one thing. And in the case of just pored foam is another.
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Old 02-11-2019, 05:40 PM
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Originally Posted by THE BARRACUDA View Post
The foam is there to control flexibility within the fiberglass. The fiberglass can hold it without the foam.

The only foam I've seen inside Boston whalers has been pored foam. I have not seen what they use on the Large 30Ft plus vessels. The foam and glass intertwined and fused together in Coosa is one thing. And in the case of just pored foam is another.
Are you aware that "oil canning", what you referred to as" flexibility within the fiberglass" is destructive to the fiberglass? If you fill a cardboard box full of pour foam does the box become more rigid? Well that works for a stringer grid or a large void in a hull also.
Chemically, the foam used to by Boston Whaler is referred to as a urethane foam, coosa it's also a urethane foam with some poorly wet out fiberglass fibers Incorporated. The coosa is considerably higher density but it's still a foam that is not very resilient, it's not ductile, it doesn't tolerate much abuse before the cells start breaking down. In the real world and particularly after fiberglass skins are applied, those fibers don't add much, it's as much a sales pitch is anything, Bills a custom yacht builder here on the forum prefers a similar product without the roving.
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Old 02-11-2019, 05:54 PM
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Originally Posted by Perthbloke View Post
Kevlacat is an Australian built boat in most instances. And a very well respected one at that. I realise a few moulds were sold to the US.

Tunnels, the pieces of crap fibreglass hulls they produce in China don't sell here due to the re-work and seaworthiness issues experienced here with them, even by the biggest factories that produce on contract for some of the overseas brands.
not exactly right, the Australian owners of Kevlacat went to the US to build them, I don't think it was a huge success so they left, and boats were made by others to a considerably lower standard, these are the ones that gave the brand the rather dubious name in the US.
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Old 02-11-2019, 07:34 PM
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Originally Posted by Perthbloke View Post
Try sending an email to info@kevlacat.com.au He's quite a nive bloke and will give good advice. Also, there is another place that specialises in the manufacture and refurbishment of cats that size. Explain to them and where you are and he will give great advice: https://www.facebook.com/Dna-Fibregl...562/?ref=br_rs
Thanks! this is good info

Originally Posted by noelm View Post

not exactly right, the Australian owners of Kevlacat went to the US to build them, I don't think it was a huge success so they left, and boats were made by others to a considerably lower standard, these are the ones that gave the brand the rather dubious name in the US.
This one is a US made Harry Carter model, according to the production year and some research I have done. The Aussie run US company and molds were then sold to another group in Georgia IIRC and the company changed names to Team Kevlacat. There are some horror stories here in THT regarding the later years under Team Kevlacat ownership and management.
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Old 02-11-2019, 08:22 PM
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That's closer to it, I have known .Harry for a very long time and remember well when he went to the US to build and promote Kevlacat, it was not long after his return he got out of the business altogether and I think one of the employees took over building them here there has been several changes over the years.
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Old 02-11-2019, 11:07 PM
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I like them as they are relatively light compared to others. I believe I met Harry at the Cactus Bar in the Singapore Airport a few years ago.
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